Method and apparatus for separating sheet materials



Oct. 8, 1963 J. H. DEW 3,106,391

METHOD AND APPARATUS FOR SEPARATING SHEET MATERIALS Filed Aug. 25, 1961 4 Sheets-Sheet 1 INVENTOR.

AIIQBNEY v BY Oct. 8, 1963 J. H. DEW 3,106,391

METHOD AND APPARATUS FOR SEPARATING SHEET MATERIALS Filed Aug. 25, 1961- 4 Sheets-Sheet 2 INV EN TOR.

ATTORNEY J. H. DEW 3, 6,391

METHOD AND APPARATUS FOR SEPARATING SHEET MATERIALS Oct. 8, 1963 N\ w M m m mu W m M y 4 w w RN w vw m m ATTORNEY Oct. 8, 1963 J. A. DEW

METHOD AND APPARATUS FOR SEPARATING SHEET MATERIALS Filed Aug. 25, 1961 Imrnn 4 Sheets-Sheet 4 INV EN TOR.

ATTORNEY United States Patent 3,106,391 METHOD AND APPARATUS FOR SEPARATING SHEET MATERIALS Joseph H. Dew, Flint, Micln, assignor to General Motors Corporation, Detroit, Mich, a corporation of Delaware Filed Aug. 25, 1961, Ser. No. 134,012 6 Claims. (Cl. 271--27) ,Ihis invention relates to a method and apparatus for separating sheet materials and more particularly to a method and apparatus for separating stacked steel plates which are heavily lubricated prior to a metal forming operation.

In modern automated metal working operations wherein large metallic sheets of steel or the like are formed by bending operations in large presses, automatic means are conventionally provided to remove a single sheet of material from a supply stack adjacent the press and to transfer the sheet. of material into position within the press. In order to maintain high rates of production, means must be provided to separate single sheets from the supply stack in a minimum amount of time and with unerring accuracy. The diffoulties involved in separation of sheetsof material which are stored in vertical stacks are well known. In metal forming operations of large parts, such as automobile body panels, the metallic blanks are heavily lubricated and, consequently, the problem of separating stacked sheets is multiplied many fold. The use of vacuum cups which are adapted to engage and remove the top sheet from a stack of sheets is a well known expedient. Although vacuum cups can successfully grip the top sheet of a stack of sheets, additional means have been required to separate the next adjacent sheets from the top sheet to facilitate rapid sheet separation and insure that only one sheet is removed at one time. In previous practice, such devices as high pressure air blasts and magnetic separating means have commonly been uti lized. In spite of many previous suggestions, the separation of stacked sheets still remains a production limiting problem. w

The purpose of this invention is to provide a new and improved sheet separating method and apparatus for removing the top sheet from a stack of sheets with improved speed and accuracy. Another purpose of this invention is to provide sheet separating means of simplified construction and utilizing a minimum number of parts. Still another purpose of this invention is to utilize conventional vacuum cup clamping devices in a more efficient manner.

Other objects and advantages of the persent invention are disclosed in the following detailed description wherein an illustrative embodiment of the present invention is described by reference to the accompanying drawings wherein;

FIGURE 1 is a side elevational view of apparatus embodying the present invention;

. FIGURE 2 is a partial elevational view taken along the line 2-2 in FIGURE 1;

FIGURE 3 is an illustration of the apparatus shown in FIGURE 2 in an operating position; FIGURE 4 is a sectional view taken along the line 4-4 in FIGURE 2;

FIGURE 5 is an enlarged partial view of thesheet separating apparatus shown in FIGURE 1; and

FIGURE 6 is a sequential illustration of the separation stacked sheets with the present invention.

Referring now to FIGURE 1', the present invention relates to an improved sheet separating mechanism designated generally at 10 which is adapted to remove the top sheet from a stack of sheets 12 so that a conventional mechanical hand 1-4 can grip the displaced top sheet and "ice move it onto a conventional sheet feeding mechanism 16 for delivery to a press. The mechanical hand 14 is supported by conventional positioning apparatus 18 which allows the sheet of material to be completely removed from the supply stack .12 and correctly positioned on the conveyor means 16. The mechanical hand and the conveyor means are mounted within a frame 20 to which the sheet separator =10 may be fixed by suitable braces 22 and located in alignment above the supply stack 12. The stack of sheets 12 is supported on a conventional table 24 having hydraulically actuated vertical adjustment means to maintain the top of the supply stack at substantially the same level at all times.

The apparatus is controlled by conventional circuitry in a conventional manner. The general sequence of operation is initiated by energization of a valve which causes air to flow past a venturi system located at the center of the vacuum cups to create a vacuum in a conventional manner. A second valve is thereafter energized to cause the vacuum cups to be extended into engagement with the top sheet of the supply stack. The second valve is then tie-energized to cause the vacuum cups to be retracted and to simultaneously remove the top sheet from the supply stack. At this time, an electrical signal is generated to cause the iron hand to be extended and to clamp onto the separated upper sheet. Another electrical signal then shuts off the airflow to the venturi system to eliminate the vacuum and release the cups from the top sheet. At this time, the iron hand control 18 is energized to remove the sheet of material form the supply stack 12 and position it on the sheet feeding means 16.

Referring now to :F-IGURES 25, the sheet separating mechanism 10 comprises a frame formed from parallelly spaced side plates 30, 3 2 which are connected by spaced cross plates 34, 36. The side plates are T-shaped and have downwardly extending support arms 38, 4% which are connected at their lower ends by a pin element 42. A power cylinder 44 is fixedly secured to the cross plate 34 and has a reciprocable piston rod 46 extending downwardly therefrom. The end of the piston rod is fixedly secured to a connecting block 4t; having a pair of horizontal pin elements 50, 52 supported between depending flanges 54, 56. Upper control link elements 5-8, 60 are rotatably mounted on the pin elements 50, 52, respectively. Each of the upper control link elements terminates in transversely extending flange portions 62, 64 through which connecting bolts or the like 66, 68 extend. Lower control link elements '70, 72 are pivotally secured at the lower ends to pin elements 74, 76 and are provided with transversely extending flange portions 78, 80 at the upper ends. The bolts 66, 68 extend through the flange portions 78, 80 and are fixedly located relative thereto by means of compression springs 82, S4 and 86, $8. The compression springs floatatively suport the lower control link ele ments relative to the upper control link elements and allow limited relative movement therebetween.

Referring now particularly to FIGURE 4, a pair of oppositely extending vacuum cup lift arms are formed by spaced parallelly extending members 96, 92 and 94, 96, respectively. 7 The inner endsof each of the members are pivotally mounted on the pin element 42 and the outer ends are connected by cross braces d8, 1%. Referring now to FIGURE 5, conventional vacuum cups 102, 104 having vacuum forming supoprt heads 106, 108 are pivotally connected to bifurcated support brackets 110, 112 which are secured to the cross braces 98, 100. Each of the vacuum cups is connected by conduits 114, 116 to vacuum producing means in a conventional manner. A

I sheet engaging and bending control shoe 118 is mounted shoe is provided with a curved surface adapted to support the area of bend of the sheet being transferred. The shoe is pivotally mounted and is, therefore, self-centering relative to the sheet being lifted. The shoe is provided with a contact surface of suiiicient length and having a large enough radius of curvature to insure suflicient support for the sheet being lifted in the bend area and to permit maximum flexure of the sheet being lifted without deformation thereof.

in order to insure that only one sheet at a time will be removed from the supply stack, special apparatus is provided to cause initial separation of the top sheet from the next adjacent sheet and to further provide a positive wedge-like action between the top sheet and the next adjacent sheet as the top sheet is flexed by the lift mechanism. The special apparatus comprises a pair of conventional pneumatic hammers 130, 132 which are connected in a conventional manner by flexible conduits to a power source. As shown in FIGURE 5, each of the pneumatic hammers is provided with a reciprocable tool 134- which is adapted to form indentations 136 in the top sheet 138 of the supply stack for a purpose to be hereinafter described. Each of the pneumatic hammers is mounted on support brackets 14%), 142 which are floattively secured to the members 90, 94 by bolts 144, 146 and compression springs 14 8, 150. The compression springs 148, 154 permit limited movement of the support brackets 149, 142 relative to the lift arms to compensate for variations in location of the top sheet of the supply stack and to allow the vacuum cups 102, 104 to be firmly positioned against the top sheet regardless of such variations. Each of the pneumatic hammers is additionally supported in 'U-shaped guide brackets 152, 154 which are secured to the brackets 14-0, 142, respectively, by similar bolt and compression spring arrangements 156, 158 which permit limited relative movement of the brackets 152, 154 relative to the support plates 14%, 142 to provide additional means to maintain flexibility of the pneumatic hammers relative to the vacuum cups.

Operation In operation and at the beginning of a sheet separation 'cycle, the lift mechanism is in the position illustrated in FIGURE 3 with the vacuum cups 102, 104 deactivated and no sheet secured thereon. At the proper time, in relation to press cycle and the sheet feeding sequence from the conveyor 16, the cylinder 44- is actuated to downwardly extend the piston rod 46 and connecting block 48, and thereby rotate the lift arms into a substantially horizontal position by pivotal movement about the pin means 42. The vacuum forming means connected to the vacuum cups through the conduits 114, 116 are simultaneously actuated so that the vacuum cups will .grippingly engage the upper surface of the top sheet of the supply stack which is maintained at a constant height by the hydraulic table. The bolt and spring connections, which support the pneumatic hammers 130, 132 relative to the lift arms, permit the lower surface of the reciprocable tool 134 to be located in surface engagement with the top sheet without interfering with the action of the vacuurn cups. When the lift mechanism has been fully extended, the pneumatic hammers 130, 132 are actuated to drive the hammer tips into the top sheet and form an indentation therein as shown at 136 in FIGURES and 6. The hammers are located outwardly of the vacuum cups along a portion of the sheets which is subsequently trimmed so that the indentations in no way blemish the finished product. As shown in FIGURE 6, actuation of the pneumatic hammers and formation of the indentations 136 cause an initial separation of the top sheet from the next adjacent sheet. After the pneumatic hammers have been actuated, the cylinder 44 is actuated to cause retraction of the piston rod 46, the connecting block 48, and the lift links so that the lift arms are pivoted upwardly about the pin means 42. The vacuum cups are securely gripped on the upper surface of the top sheet and lift and flex the upper sheet as illustrated in FIGURE 3. During the first portion of the upward movement, the indentations in the top sheet are horizontally displaced relative to the next adjacent sheet to provide a positive wedging action therebetween as shown in FIGURE 6. This is because the surface attraction between adjacent sheets will cause the next adjacent sheet to momentarily hang onto the top sheet as it is lifted and flexed. However, since the top sheet is being flexed about a shorter radius than the next adjacent sheet, there will be a sliding action between the top surface of the next adjacent sheet and the bottom surface of the top sheet. This sliding action causes a horizontal displacement of the indentations 36 producing the wedging action. This action is particularly useful when the sheets are oily and have a much greater surface attraction than if they were dry. Continued upward movement of the lift arms increases the pivotal displacement of the vacuum cups from the original substantially horizontal position and flexes the top sheet about the shoe 120. When the lift arm has been fully retracted, the iron hand 14 clamps the adjacent edge of the top sheet and the vacuum in cups 102, 104 is dissipated so that the sheet may be removed by the iron hand.

The present apparatus has several advantages and specific areas of improvement over the prior art which should be noted. A comparison of the subject apparatus with prior apparatus will show that a substantial simplification and reduction in the number of parts required for successful separation of stacked sheets has been attained. Only one operating cylinder is required and a plurality of vacuum cups are operated thereby. In the prior art, blank separators commonly used independent air cylinders for each of the vacuum cups utilized. Furthermore, the attainable degree of flexing of the top sheet to obtain complete disassociation from the next adjacent sheets has been greatly increased by the present apparatus. The provision of a common pivotal axis for the pivotally mounted lift arms permits flexing of the sheet to a degree heretofore unknown. It is apparent that the greater the flexure of the top sheet, the more readily the top sheet is disassociated from the next adjacent sheets. Furthermore, in prior art devices, the vacuum cup lift mechanisms were arranged in a manner such that a sliding action of the vacuum cups relative to the surface of the sheet being lifted was encountered during the separating operation. In the present apparatus, there is no sliding of the sheet being separated relative to the vacuum cups because of the special design of the lift mechanism. With the present apparatus, the sheets to be separated can be flexed to their elastic limit to facilitate separation of adjacent sheets. It is even contemplated that in some instances the sheets may be flexed beyond their elastic limit, if necessary, to obtain satisfactory separation of the sheet when a slight deformation in the sheets will not affect the finished product.

The provision of the pneumatic hammers, which are integrally associated with the lift arms and produce a new cooperative result in combination therewith, is a most important feature of the invention. The pneumatic hammers are mounted in a manner to eliminate any interference with the function of the vacuum cups 102, 104. By providing indentations in the top sheet, a positive wedging separation of the top sheet from the next adjacent sheet is obtained as the lift arms are retracted and the sheet is initially flexed. In dealing with heavily lubricated sheets, the positive wedging action breaks the lubricant film between the top sheet and the next adjacent sheet so that the sheets may be more readily separated. Those skilled in the art will readily appreciate the difliculties encountered in separating heavily lubricated sheets and the importance of breaking the lubricant film so that the sheet adjacent the top sheet is not carried upwardly when the upper sheet is removed by the vacuum cups.

It is to be understood that the aforedescribed apparatus is merely illustrative in many of the details of construction and the arrangements of the various parts. Insofar as the advantages of the present invention can be obtained by obvious modifications, such modifications are intended to be included within the scope of the appended claims, except insofar as limited by the prior art,

I claim:

1. Means for separating sheet material comprising a pair of oppositely extending lift arms, said lift arms being mounted on a common axis, constituting a stationary pivot, sheet gripping means provided on the ends of said lift arms, a single actuating means for pivotally moving said lift arms about said common axis from a first position of engagement with the top of a sheet of material supported on a stack of sheets to a second position pivotally displaced towamd one another whereat the sheet is separated from the stack of sheets, and control linkage interconnecting said actuating means and said lift arms to positively displace said lift arms between said positions.

2. In apparatus for separating the top sheet from a stack of sheets, a pair of pivotally mounted oppositely extending lift arms, said lift arms being pivoted about a common axis for movement between a first position substantially parallel to said stack of sheets and a second position pivot-ally inclined toward one another and relative to said stack of sheets, vacuum cup means associated with each of said lift arms to engage and lift sheets from said stack of sheets, a single power cylinder to simultaneously actuate said lift arms between said positions, controllinkage extending between said power cylinder and said lift arms, pneumatic hammers secured to and carried by said arms, and said pneumatic hammers having means to form indentations in the top sheet prior to movement of said lift arms from said second position .to said first position to provide a positive wedging action between the top sheet and the next adjacent sheet of the stack of sheets as said lift arms are moved from said first position to said second position.

3. The apparatus as defined'in claim 2 and wherein said pneumatic hammers are connected to said lift arms by cushioning means which permit limit-ed relative displacement of the pneumatic hammers relative to the lifting arms to eliminate interference of the pneumatic hammars with the operation of said vacuum cups.

4. The apparatus as defined in claim 2 and wherein shoe means are mounted coaxially with said lift arms to engage said sheet and control fiex-ure thereof during movement of said lift arm-s from said first position to said second position.

5. The apparatus as defined in claim 2 and wherein said link means includes lost motion spring connections to compensate for variations in the amount of pivotal movement of said lift arms needed to obtain a predetermined amount of flexure in said sheet.

6. The method of removing the top sheet from a stack of sheets, said sheets characterized by being permanently locally deformable when a localized impact force is applied thereto and comprising the steps of: striking the top sheet on the upper surface thereof with a deforming tool so as to produce a localized deformation therein, said localized deformation being of sufficient penetration to also deform the bottom surface of said top sheet thereby locally separating same from the next adjacent sheet, flexing said top sheet and necessarily the next adjacent sheet when the surface attraction therebetween is sufficient to cause them to hang together and sliding the localized deformation of the top sheet relative to the next adjacent sheet causing a positive wedging action be tween the top sheet and the next adjacent sheet by horizontal displacement of the deformation relative to the next adjacent sheet, and removing said top sheet from the stack without removing the next adjacent sheet.

References Cited in the file of this patent UNITED STATES PATENTS 853,910 Tyden May 14, 1907 1,911,884 Darbaker May 30, 1933 2,406,766 Harrold Sept. 3, 1946 2,941,799 Reincke June 21, 1960 3,033,562 Dretz May 8, 1962 

1. MEANS FOR SEPARATING SHEET MATERIAL COMPRISING A PAIR OF OPPOSITELY EXTENDING LIFT ARMS, SAID LIFT ARMS BEING MOUNTED ON A COMMON AXIS, CONSTITUTING A STATIONARY PIVOT, SHEET GRIPPING MEANS PROVIDED ON THE ENDS OF SAID LIFT ARMS, A SINGLE ACTUATING MEANS FOR PIVOTALLY MOVING SAID LIFT ARMS ABOUT SAID COMMON AXIS FROM A FIRST POSITION OF ENGAGEMENT WITH TOP OF A SHEET OF MATERIAL SUPPORTED ON A STACK OF SHEETS TO A SECOND POSITION PIVOTALLY DISPLACED TOWARD ONE ANOTHER WHEREAT THE SHEET IS SEPARATED FROM THE STACK OF SHEETS, AND CONTROL LINKAGE INTERCONNECTING SAID ACTUATING MEANS AND SAID LIFT ARMS TO POSITION DISPLACE SAID LIFT ARMS BETWEEN SAID POSITIONS. 